1. Field of the Invention
The present invention relates to an IC tag, a reader/writer for the IC tag and a system using the IC tag. More particularly, the present invention relates to an IC tag which has a means for recording and erasing invisible information and a means for recording and erasing visible information, both allowing recording and erasing information in a non-contact manner, exhibits flexibility and can have a small size, a reader/writer for an IC tag which can erase and record information in both of the means for recording and erasing invisible information and the means for recording and erasing visible information in the IC tag using the same apparatus in a non-contact manner, and a system using the IC tag which can be applied to logistics management.
2. Description of Related Art
As labels used for control of articles such as labels attached to plastic containers for transportation of foods (good-delivery boxes), labels used for control of electronic parts and labels for logistics management attached to cardboard boxes, heretofore, labels using a heat sensitive recording material (such as a direct thermal paper) as the surface substrate have been mainly used. In the heat sensitive recording material, a heat sensitive recording layer containing an electron-donating dye precursor which is, in general, colorless or lightly colored and an electron-accepting color developing agent as the main components is formed on a support. By heating the heat sensitive recording material by a heated head or a heated pen, the dye precursor and the color developing agent react instantaneously with each other, and a recording image can be obtained. Once the image is formed, it is impossible that the image in the heat sensitive recording material described above is erased to restore the condition before being treated for the image formation.
Heretofore, a heat sensitive recording material of the contact type described above is used as the surface substrate in the labels used for the logistics management of articles described above, and information such as the address, the name of the sender, the name of the article, the number of the article and the lot number or a bar code expressing the information is printed using a thermal printer of the contact type, and the obtained label is attached to the adherend. When the object assigned to the label is achieved, the label is manually removed so the adherend such as the container and the card board box can be utilized again, and great amounts of time and labor were required for the removal. To the adherend from which the label has been removed, another label printed by a thermal printer of the contact type is attached, and the adherend is used again.
As described above, it is the actual situation at present that a label is removed and another label is attached every time an adherent is reused. Therefore, a rewritable thermal label which can be repeatedly used for recording and erasing information while the label is not removed from the adherend in each reuse of the adherend but remains attached to the adherent is attracting attention. For example, a reversible heat sensitive recording material of the non-contact type having a means for recording and erasing visible information which is obtained by forming a heat sensitive color developing layer containing a dye precursor and a reversible color developing agent on a support is developed (for example, refer to Patent Reference 1). Although this reversible heat sensitive recording material of the non-contact type exhibits flexibility, the information which can be recorded depends on the size of the label, and the amount of the information is limited. For the reversible heat sensitive recording material of the non-contact type described above, in general, laser beam is used for recording information. For erasure of information, in general, laser beam and/or heat is used.
On the other hand, a tag using an IC for wireless communication having a rewritable memory device, which is called an IC tag, is attracting attention. In general, the IC tag has no source of electricity by itself, and the IC tag and a reading apparatus communicate with each other on demand by the reading apparatus.
The IC tag has electronic information at the inside of the tag attached to an “article” and has the function of identifying the information of the “article” by communication with the reading apparatus through radio wave. In comparison with conventional bar codes, the IC tag has the characteristics in that (1) the amount of information held by the IC tag is greater, (2) the tag can be recognized at a separated position (even when the tag is not seen directly), (3) many tags can be recognized simultaneously, and (4) an information in the tag can be replaced with another information, in some cases.
The IC tag described above can be utilized, for example, control at the place of production and in the stages of logistics, sales and recycling and disposal and for the logistics management.
An IC tag has, in general, a means for recording and erasing invisible information of the non-contact type constituted with an IC chip and an antenna circuit connected to the IC chip. An IC chip can be used more conveniently when the IC chip further has a means for recording and erasing visible information of the non-contact type. In this case, it is important that the functions as the tag, i.e., the flexibility and the small size, are not adversely affected.
A medium for display and recording having a means for digital information recording which records information and can rewrite the recorded information in a non-contact manner and a means for displaying information which displays information and can change the displayed information into another information in a non-contact manner, is disclosed (for example, refer to Patent Reference 2). In this medium for display and recording, the means for displaying information is constituted with a member for displaying information which is formed by laminating a display layer having the function of memory and a photoconductive layer comprising a photoconductive material between a pair of opposite electrodes at least one of which transmits light and a member for digital information recording which comprises, for example, an IC memory of the non-contact type. However, the above medium for display and recording is provided for use as a planar display and has a drawback in that the medium is inconvenient for use as a tag since the medium is rigid and poor in flexibility and has a great size due to great sizes of characters in the display portion.
[Patent Reference 1] Japanese Patent Application Laid-Open No. 2003-118238
[Patent Reference 2] Japanese Patent Application Laid-Open No. 2004-102432